Water conditioners generally have a mineral tank containing a bed of an ion exchange resin, such as a polystyrene resin. Most ion exchange resins are insoluble and act as permanent anions (i.e., ions with negative charges) to which exchangeable sodium ions (Na.sup.+) can attach. When a water conditioning system is in service, raw untreated water (i.e. hard water), containing mineral ions such as calcium ions (Ca.sup.++) and magnesium ions (Mg.sup.++), is fed into the mineral tank typically at a location above the bed of ion exchange resin. A riser tube or standpipe in the mineral tank provides an outlet for water that has been filtered through and conditioned by the resin bed (i.e., the standpipe is an outlet for soft water). Filtering raw water through the ion exchange resin filters out non-ionic debris to remove turbidity in the water. Also, hard water passes through the ion exchange resin, the calcium (Ca.sup.++) and magnesium (Mg.sup.++) ions in the hard water displace the sodium ions (Na.sup.+) from the ion exchange resin. The calcium (Ca++) and magnesium (Mg.sup.++) ions have a greater affinity for the resin than do the sodium ions (Na.sup.+). In this manner, the offensive hardening ions (i.e. Ca.sup.++ and Mg.sup.++) are replaced in the water by a chemically equivalent concentration of sodium ions (Na.sup.+).
The conditioning or softening process continues until the initial supply of sodium ions (Na.sup.+) in the ion exchange resin is depleted to a point that the hardening ions (Ca.sup.++) and (Mg.sup.++) are no longer effectively removed. At this point, hardness begins to appear in the water exiting the system, and the ion exchange resin is considered exhausted.
Although calcium (Ca.sup.++) and magnesium (Mg.sup.++) ions have a greater affinity for the ion exchange resin than do sodium ions (Na.sup.+), the chemical reaction can be reversed if a high enough concentration of sodium ions (Na.sup.+) are introduced to the ion exchange resin. An exhausted, or partially exhausted ion exchange resin can therefore be regenerated by introducing a solution of common salt (i.e. sodium chloride, NaCl) into the mineral tank.
Water conditioning systems operate in a service cycle and a regeneration cycle. In the service cycle, untreated raw water flows down through the mineral tank and up through the standpipe for use. The water is conditioned/filtered when passing through the mineral tank. When the water conditioner is taken out of service for the regeneration cycle, raw water for residential use bypasses the mineral tank untreated.
The regeneration cycle includes three modes: a backwash mode, a brine/slow rinse mode, and a fast rinse/brine refill mode. In the backwash mode, water flows down through the standpipe in the mineral tank and up through the ion exchange resin bed. Debris and/or filtered material in the resin bed are flushed from the bed during the backwash mode. In the brine/slow rinse mode, a brine solution is drawn from a brine tank into the mineral tank, and flows down through the resin bed and up through the standpipe. This process regenerates the ion exchange resin. Typically, brine is drawn from the brine tank until an air check in the brine tank closes. Once the air check closes, the system switches to a slow rinse mode. The slow rinse mode consists of a slow flow of water through the mineral tank down through the ion exchange resin and up through the standpipe. In the fast rinse/brine refill mode, water is flushed through the mineral tank down through the ion exchange resin and up through the standpipe to remove any remaining brine in the mineral tank. Usually, the brine tank is refilled with water at the same time.
Most water conditioning systems include complicated valve systems to provide for these multiple cycles that are necessary to regenerate a water conditioning system. Years ago the valve systems were controlled manually, but now mechanical and electronic control systems are available to control the operation of these complicated valve systems. In many applications, control systems improve the effectiveness, efficiency and convenience of water conditioning systems.
Since the water conditioner must be taken out of service for the regeneration cycle (i.e. backwash, brine/slow rinse, fast rinse/brine refill), it is normally desirable to start the regeneration cycle at a predetermined time of day such as 2:00 AM when it is unlikely that there will be a demand for conditioned water. Automatic control systems provide a convenient way to start regeneration at 2:00 AM.
Some water conditioning systems have controls that set the start of the regeneration cycle after a fixed number of days (i.e. an interval regeneration scheme), while others set the start of the regeneration cycle on selected days of the week (i.e. a dayof-the-week scheme). Still other water conditioning systems have controls that monitor the volume of conditioned water used, and start the regeneration cycle at the selected predetermined time (e.g. 2:00 AM) on the day following the day in which water usage exceeds a preset water usage limit (i.e. a demand regeneration scheme). Water conditioners implementing a demand regeneration scheme tend to make consistent effective use of salt in the brine tank if properly programmed for the particular application.
It is desirable that the control system be easy for a technician to customize to a particular application. It is also desirable that the control system be convenient for lay people to make simple adjustments.
In general, mechanical controls for water conditioner valve systems can be cumbersome, and can also have durability problems. On the other hand, while fully electronic systems can be customized, fully electronic systems tend to be expensive. In addition, key pad displays for fully electronic systems can also be confusing and difficult for lay people to program.